Addiction can be defined as a loss of control of substance use despite adverse consequences. Addiction to legal and illegal substances destroys the lives of both addicted subjects and their families, exerting an enormous cost and burden on society. The molecular- and cellular-based mechanisms that contribute to the initiation and development of addiction remain to be elucidated. Estimates have suggested that 40-60% of the vulnerability to addiction may be attributable to genetic aberrations. Multiple chromosomal regions have been linked to addiction including those containing the dopamine transporter (DAT) and vesicular monoamine transporter (VMAT2) genes. Current efforts to understand how polymorphisms in these monoamine transporters contribute to the molecular mechanisms of addiction are severely hindered by the inability to directly interrogate neural cell types from the patients. Patient-specific sources of cells carrying specific genetic variants that are capable of robust and reproducible differentiation into specific neural lineages do not exist. We propose to develop a cell-based system whereby neural cells from afflicted individuals can be functionally assayed to interrogate the molecular mechanisms underlying addiction. To achieve this goal we have developed a cutting-edge proposal that that incorporates the skill and expertise of multiple disciplines. In Aim 1 we will derive and characterize patient-specific, induced pluripotent stem (iPS) cells from addiction patients and controls that carry monoamine transporter polymorphisms. Since midbrain dopaminergic system play a prominent role in natural and drug related reward pathways and represent a common substrate for drugs of abuse, in Aim 2 we will differentiate patient-specific iPS cells line into dopaminergic neurons and carry out a detailed and functional characterization of these cells to identify their molecular characteristics (i.e. A9, A10, mesolimbic or mesocortical dopaminergic neurons). In Aim 3, we will characterize, compare, and functionally assay these patient-specific, iPS cell-derived dopaminergic neurons from control and addiction patients that carry polymorphisms for hDAT1 and hVMAT2 gene. There is great potential for patient-specific iPS cell technology to profoundly impact our understanding of human development and disease by providing genetically distinct, functional sources of human cells. By completing the aims set forth in this proposal we expect to provide a detailed characterization of dopaminergic neurotransmission function in patients afflicted with addiction and provide insight into the pathophysiology of this complex disease as well as the contribution of genetic variants in monoamine transporter genes to addiction. We have established an interdisciplinary team that combines strengths in ethnographic study of drug addicts, neural differentiation and dopaminergic function analysis, as well as pluripotency and iPS cells to interrogate novel questions about the cellular and molecular dysfunction that contributes to addiction. We expect that results from our studies will have immediate relevance to the understanding and treatment of this human disease.